The present invention relates generally to a mounting and protective cage for a fuel tank that is mounted between the side members of a vehicle such as a school bus.
An objective of this invention is to provide a vehicle, such as a school bus, with a large fuel tank, in the 100 gallon capacity range, that will be protected in the event of a crash, even at impact speeds of up to 30 mph from any direction, and otherwise meet Section 301 of the Federal Motor Vehicle Safety Standards. The fuel tank mounting and protective cage of this invention is intended to provide this degree of protection for any of the several combinations of suspension systems and tires that may be offered by the manufacturer of the vehicle chassis.
The side members or frames of vehicles, such as school buses, are constructed of substantial C-shaped steel beams. The area between these C-shaped steel beams or side members is thus well protected. Much of this protected area is already occupied by the exhaust system, the drive to the rear axle and the brake lines. However, a portion of this protected area rearward of the rear axle is available to receive a fuel tank.
The vehicle floor extends across the top flange of the side members and thus the fuel tank can not extend above the side members. Thus, to accommodate a 100 gallon fuel tank rearward of the rear axle, the tank must extend below the lower flange of the side members. However, there are limits to the distance below the side members and the distance to the rear of the vehicle that the fuel tank and its protective cage can extend.
The angle between the ground line and a line extending from the ground/tire interface of a rear tire and the lower edge of the rear bumper is called the departure angle. Nothing should extend down from the underside of the vehicle that violates the plane of this departure angle. Stated in another way, when the front wheels of a vehicle encounter an incline and the rear bumper moves toward the pavement, the rear bumper should scrape the pavement before anything else that extends down from the underside of the vehicle. Thus, the location of the bottom rear lateral edge of the mounting and protective cage is limited by the angle of departure.
The ease of assembly of the protective cage to the vehicle chassis and removal from the chassis for service are important attributes of this invention. Since the areas outwardly of the side members may be used for luggage compartments, the outer surfaces of the side members become inaccessible after installing the bus body and luggage compartments. Thus, removing the fuel tank for service must be possible without access to the bolts or other connecting devices that are located on the outer surfaces of the side members.
FIG. 1 illustrates a prior art mounting and protective cage for a fuel tank 10 that is mounted between the side members 12. It is apparent from FIG. 1 that, if this prior art device is struck with sufficient force at the location indicated by the arrow A in this view, the sheet metal liners 14 will bend causing the fuel tank 10 to shift and collide with the mounting and protective cage. The steel beams 28 that connect the lower edges of the liners 14 and extend laterally under the fuel tank 10 and the end plate 18 may shift, as a parallelogram, in the event of a side crash. This parallelogram type movement is permitted because the joint between the sheet metal liners 14 and the steel beams 28 has very little resistance to bending. This joint is formed by a bend 15 in the sheet metal liners 14 which can be bent in either direction. Thus, this prior art protective cage may be vulnerable in situations in which a side crash impacts below the lower flange of the side members.
For the foregoing reasons, there is a need for a fuel tank protective cage for mounting a fuel tank of the type that extends between and below the vehicle side members that protects the fuel tank from crashes that impact the protective cage below the lower flanges of the vehicle side members.